Crossbar tandem office for telephone systems



Nov. 3, 1953 w. T. HAINES ET A1.

CROSSBAR TANDEM OFFICE FOR TELEPHONE SYSTEMS Filed Nov. 17. 1948 9Sheets-Sme?l l Nov. 3, 1953 w. T. HAINES ET Al.

CROSSBAR TANDEM OFFICE FOR TELEPHONE SYSTEMS 9 Sheets-Shee'fl 2 FiledNov. 17, 1948 W 'r HAM/E5 /NVE/vro/es: J B NEWSOM @y n, d? Arrows/EVNov. 3, 1953 w. T. HAINES ET Al.

CFOSSBAR TANDEM OFFICE FOR TELEPHONE SYSTEMS 9 Sheets-Sheet 5 Filed NOV.17. 1948 n4 't HAM/E5 /NVEN7'0H$:JU B. NEWSOM ATTORNF" Nov. 3, 1953 W.T. HAINES ET Al.

cRoSSBAR TANDEM OFFICE FOR TELEPHONE SYSTEMS 9 Sheets-Sheet 4 Filed NOV.17, 1948 llmmN UNN W THA/NES By 'J B. /VEWSOM ATTORNEY Nov. 3, 1953 w.T. HAINES ET Al.

CROSSBAR TANDEM OFFICE FOR TELEPHONE SYSTEMS 9 Sheets-Sheet 5 Filed Nov.17. 1948 W THA/NES /A/l/EA/ros.J 3 NEM/SOM By W Arrow/5V Nov. 3, 1953 w.T. HAINES ET AL 2,658,108

CROSSBAR TANDEM OFFICE FOR TELEPHONE SYSTEMS Filed Nov. 17, 1948 9Sheets-Sheet 6 W'ZHA/NES /Nz/ENTCRS. J NEWSOM www ATTORNEY Nov. 3, 1953w. T. HAlNl-:S ET AL CROSSBAR TANDEM OFFICE FOR TELEPHNE SYSTEMS 9Sheets-Sheet Filed Nov. 17. 1948 ATTORNEY Nov. 3, 1953 w. T. HAINES ETAL 2,658,108

CROSSBAR TANDEM OFFICE FOR TELEPHONE SYSTEMS Filed Nov. 17. 1948 v 9Sheets-Sheet 8 W IHA/NES /NVENTORS' J. 5. NEWSOM ATTORNEY Nov. 3, 1953w. T. HAlNEs ET AL 2,658,108

cRossBAR TANDEM OFFICE FOR TELEPHONE SYSTEMS Filed Nov. 17, 1948 9Sheets-Sheet 9 W 7.' HAI/VES /A/l/E/VTORS.J B. NEWSOM By '9k/J PatentedNov. 3, 1953 UNITED STA-TES toy Bell Telephone; Laboratories;Inco;mirategi1 New York, N. Y., a corporation of New York ApplicationNovember 17, 1948; Ser ialNo.g6,05.02,"-

(Clt. 159e-163 13 Claims;`

invention relates to telephonesystems, and more particularlytoequipment'in a tandemv oice.

Oiices rWithin an exchange -area may`r be intercennected eitherbyIdirect trunks or ley-trunksf extending through a tandem oice. Whetherdirect trunksor tandem'trunks are providedlfor use inv a particularconnectionv is primarily a question of trafcdensity, although tandemtrunking mayY also serve to supplement direct trunking;

When vtwo oiiices are connected 'through' a cross bartandem oice; thetandem sender must be capable -of receiving, registering,landtransmitting tothe tandem marker not only two and-three'- digit'designationssof terminatingoffices, but also a seriesof 1special codesdesigned to accomplish special` functions inconnection with intertolldialing.

An object of the present invention is'to provideA a tandemsendercapablel of distinguishing between, registering, and transmittingto the marker three-digitVV and two-digit oce codes;

Anotherobjeet offthe invention is4 to provide atandem sender capable ofregistering and ing twordigitflX codes-andthree-digit TX' codesy fromVeach.- other and. froml other codes. received.

Inf general, these objectsA have been` attained' by providngthe-ztandem,sender witha seriesoi:`

digit registers designated A, B, C, thousands;- hundreds, tens, units,and stations. The.; input leads, tothe tandem sender are sequentiallyoon.-A nected to these several registers by means of a= pair of Walkingrelays associatedwith each of.y the digit registers. counting relays areprovided.

The three digits of a three-digit office-code arev registered on the'A,B and C digit registers, respectively. Means responsive to theregistration ofthe third digit are arrangedto connect leads from eachofthe A, Band Cidigit registers to the marker whereby' the threen digitsofthe olice codeA maybeY transmitted to the marker;

The two digits of-a two-digit oi'ce code are registered ion-the -A and Bdigit registers, respectively, and meansare provided, responsive-tovtheV specific digits ,preselected` as two-digit office code Inaddition, twoy pairs of,

Y 2; indices,- to-efEectivel-y-lbypassthe G-fdigit-reg'isters Thesemeans also function;v responsive? tol the registrationoff the secondfdigit, to connect-leads from the A digit' registeritothermarker, to'imipress on-those leads normally associatedwith'the B digit register varepresentation of# thedig`itl0," and to connect-to the-B digitregisterthose leads normally associated with the` CY digit' registerwhereby the'two` digits-- of atwo-digit! o'i'ceoode.

: maybe transmitted.to'themarker as? athreedigit code with0las-thesecon'ddigit;

A vservice-code is-atwodigitfcode prexed by* the digit 1'." Theiniti-al'digiti-1y is registered on thefirst pair of counting relaysand theftwoIdigits of the service code -are registered? onv the Av and B1 digitfregisters; respectively; The-first pair of counting relays is arrangedto function incooperation with@ mea-ns'responsiveto a' start signal fromthe `originating operator, tol impress on those leads-normallyassociated-with the-'AV digit register Y arepresentation y of thevrdigit -Y 1; and to operatefadditionalmeans-toconnect-to the A1v digitvregisterthose 1 leads normally associated with the Bf' digityregistergvandfto connect toY the :B digit register those-leads=normallyf associatedv1 with the@ Cy digitl' register-f# wherebyl` theservicecode is'- transmitted to' the lmarkerg asa three-digitcode withY1as the-initial digit.

A' 'I'X= codeJ isa two-digitfor three-digitv code prexedf by the digits1.1i The initial digits 11 area registeredx onthe two pairs of'countingrelays, respectively, and' 1 the twol or three i digits of the TX codeare registeredu in the A andi B; or A, B^andC Adigit*registers;respectively. A two-digitLA TX; code; is transmitted to the marker,in-thelsame manner as is a service0/ode,v anda three-digtTX corde' isltransmitted' to )the marker in, thei same manner; ask a threefdigit;ofce' code; Means associatedwiththe secondjpair of' counting relays arearranged to vindicate :toV the marker'tlia't a 'IXicode isbeir'igt'ra'nsmitted.

Theinvention may be more' clearly. understood from'a consideration oflthe following description x with referencetothe accompanying drawings;in; which:

controller', circuit, andzaftrunlelinleand connectonv connecting; with".trunks to ai; plurality. off ten-1 minatng oces i Figs. 2 to 9 showportions,orthetanclem;senderI Ofzwhihi Y Figs;` Ziand Bshowrthelcountingrelays, wal-kk ing relays, and relays for distinguishing thetype of code received;

Figs. 4 and 6 show the A and AA digit registers;

Figs. 5 and 7 show the B and C digit registers;

Figs. 8 and 9 show the relays for associating the tandem sender digitregisters with the marker, and, diagrammatically, a marker and a markerconnector; and l Fig. 10 shows the manner of arranging Figs. 1 to 9.

No details of the originating and terminating oices or of much of theequipment immediately associated with the tandem sender have been shown.Portions of the tandem sender not essential to the present disclosurehave been omitted. Reference is here made to the tandem telephone systemdisclosed in Patent 2,281,636, granted May 5, 1942, to W. B. Stricklerand to the patents therein referred to for a'complete disclosure of theportions of a suitable telephone system not shown n detail herein. Y

, The thousands, hundreds, tens, units, and stations digit registers andassociated walking relays have been omitted from the drawings forpurposes of clarity.

Throughout the following description, functional reference charactershave been used to identify the relays and certain of the leads. Therelay designations are followed by a number in parentheses representingthe gure oi the drawingdin which that relay appears, for example, relayON,I(2) appears in Fig. 2 and has as its major` function the control ofcertain ofi-normal grounds. The location of the functionally designatedleads is believed to be apparent from the context.

Referring now to Fig. l of the drawings, the

calling ysubscriber establishes a connection to the operators positionwithin his dialing area by any well known ,means and informs theoperator ofthe designations of the desired oi'llce and station ordesiredspecial code. Upon determining that the desired destination maybereached through a tandem oice, the operator selects an available trunkTR which extends through test jack JA( I) to conductors T and R of thetandem orhce trunk circuit.A The operator is provided with arkey-set KS(I which-in the preferred embodiment of the invention, may be of themultifrequency type as disclosed, for4 example,l in Patent 2,332,912,granted October 26, 1943, to G. Hecht et al.

When the tandem trunk circuit of Fig. l is seized', relay A( I) `isoperated over a circuit from battery at the'originating oice over thering conductor of the trunk, lower normal contacts of test jack JAG),conductor R, conductor IGI,

No. 8 contact of relay Dl (I), conductor 5I82, No.D

1 contact of relay'T( I conductor 83, conductor I 94, lowerwinding' ofrelay A( I `tdg'rund. Relay A( I in operating, closes a circuit fromground', contact of relay A( I conductor |65, No. 2 contact of relayD,(`I conductor IG, No.1 contact of relay D2(I)`, conductor ST and tothesender link. The sender link then functions' to connect an' idlersenderof the proper type to vthe tandem trunk circuit of Fig. 1. fAs will behereinafter explained, the senderis arranged', in re-V sponseto itsseizure, to connect ground over conductor- CO, winding of relay/T(I),to' battery.v

nects ground over the sleeve lead SI to the hold magnets of the linkswitches, when later operated, over a path from ground, No. 4 contact ofrelay T(I), conductor 91, No. I contact of relay F(i) and sleeve leadSI. The normally complete circuit from ground, No. 5 contact of relay T(I conductor IGS, No. I0 contact of relay DI (I) to lead PB is alsointerrupted upon the operation of relay T(I). Lead PB is provided topermit connection to a traic register circuit which may be of the typedisclosed in Patent 2,274,083, granted February 24, 1942, to C. G.Miller.

When relay A(I) releases, the above-traced path over which ground isconnected to the ST lead is interrupted at the No. I contact of relayAH), and the removal of this ground allows the sender to complete itsfunctions.

At this time the TI, RI and SI leads are connected to the trunk link andconnector (Fig. 1), and the D, FT, FR, DC, T, R, CO and ST leads areconnected through the sender link and controller circuit to themultifrequency pulsing receiving circuit shown diagrammatically in Fig.2. A suitable type of multifrequency pulsing receiving circuit isdisclosed in the above-cited patent to Hecht et al.

When the sender is seized by the sender` link and controller circuit toserve a call, elements of the sender (not shown) immediately registerthe trunk link frame number and the class of service in the well-knownmanner. When this initial registration has been completed, the senderlink (Fig. 1), after making a test to guard against a double connection,grounds common lead GS thus operating relay ONI (2). Relay ONI (2), uponoperating, locks itself to ground over its No. 3 Contact, connectssupply ground through its Nos. 4 and 5 contacts to off-normal groundleads GDI and GD2, respectively, and closes a circuit from ground, No. 2Acontact of relay ONI (2), conductor 295, Winding of relay ON3(2), andto battery, thereby operating relay ON3(2). Relay ONI (2) also connectsground through its No. l contact to the CO lead to operate relay T(I) inthe tandem trunk circuit as was previously mentioned.

Relay ON3(2), in operating, connects battery through its Nos. 3, 4 and 5contacts, and over leads BATI, BAT2, and BATS to the multifrequencypulsing receiving circuit. Battery is also conducted through the No. 6contact of relay ON3(2) over conductor 204, and through resistanceAH(2), biasing winding of relay TU(2) to ofi-normal ground lead GDI. Thebiasing winding of relay T(2) is thereby energized to ensure that relayT(2) is closed on its back contact by the time any pulsing frequenciesare received in the multifrequency pulsing receiving circuit.

In general, the sender is provided with eight digit registers of iiverelays each wherein the A, B, C, thousands, hundreds, tens, units, andstations digits may be registered'. The digit register for the A digitcomprises relays AMS) AI (6),A2(6), A4(4) and A101). The digit registerfor the B digit comprises relays Bll(1) BI (1), B2(1), BME) and B1(5).The digit register for the C digit comprises the relays CM1). CM1),02(1), 04(5) and 01(5). Similarly, thousands, hundreds, tens, units, andstations digit registers are provided, although they have been omittedfrom the drawingsfor the sake of clarity. In some cases auxiliary relaysare required to provide sufficient contacts, as, for examplein the caseof the A digit register in which auxilcesegioes iary relays- AOMS), A'iIVIV(it), A'ZAXA), A4AK4'), andj AIAUI) are provided.'

Theffregistration leadsl froinlthe receiving: cir@- cuit;aretransferredsuccessively from digitV to digitvbyfmeans of a-Walkingcircuitcomprising agpainofrelays per digiti register. Digit register Aisprovidedwith walkingrelaysAAQ- and` AB(2) digit register B is providedvvitlfi-walk-v A'A(2`-) in'k series, to'battery. Relays'ABQ) andv AA` 2therefore operate and lock overvthe No. I' contactof relay AB(2") andconductor 2025? to offlnormal ground lead GD3. Relay ABQ), inioperating,closesv ground fromoi-normal ground lead GD3', No. 2VK contactofrelayAB(2), con ductor203, through the Winding of relays BB(3) and BA(3) inseries, and to battery. Relays- BB(3") and BA(3) operate and lock overvthe No. I'contact of relay BB(3) to off-normal groundl leadvr GD3. RelayBB(3), in operating, closes ground fromr off-normal ground lead GDS, No.I- and No, 2 contacts of relay BB-(3), conductor 30|, winding of relay(3B-(3i, conductor 352, No. .l-contactofi relay TD(3), conductor 333,Winding of relay CA(3), and to battery. Relays CB(3) and CAG)operate'and lock to off-normal ground lead'GDS over'the No.l `li'contactof relay CB(3). Similarly,- the walkingrelays associated With thethousands, hundreds, tens, units and stations digit registers areprogressively energized and locked.

When the SB(3) walking relay associated With the final-or stations digitregister is operated in response to the operation of thewalkingrelaysassociated With the units digit register, ground is connected throughthe depicted con'- tact of relay SB(3`), conductor 304-, conductor 305,No. 5 contact of relay O-E(3), conductor 306Winding ofrelay RVI (3) tobattery. Relay RVI(3), in operating, reverses the'battery andi groundconnections to ther T2V and R2 leads' through the multifrequency pulsingreceiving circuit', through the tandem trunk circuit' and over thektrunk TRU). This reversed battery is a signal to the originatingoperator that registration pulsing may begin.

'I'he operation of the RVI (3)` relay also closes" the loop to the J andL leads to the multifrequencypulsing receiving circuit shown in Fig; 2.This circuit may be traced inV part' from the J lead at themultifrequency pulsing receiving, cir-1V cuit, No. I contact of operatedrelay ON3(2), left-handcontact of vrelay T0(2), conductor'242, No'. Ivcontact of. relay RVI(3), No. I contact' of relay ST(3), No. 3contact'ofrelay OE(3), over. the L lead to' the multifrequency pulsingref-V ceiving circuit in' Fig, 2.' This J-L loop isl in series with theprimary windings of the channel relays in the multifrequency receivingcircuit and renders those relays operative when pulses ofithe; correctfrequencies are receivedv fromthe originating` operators key-set. Thispath alsol subsequently acts Aas allocking-path for the chan-vv nel.relays. Y i

When. they originatingw operator-" receives the reversed batterystartpulsing signal, shedepressesthe KP" key, in themultifrequency9111s? ing key-set KS( I )i thereby. transmitting. a..Kl?. signaltoprepare. the receiving circuit to receive multifrequency pulses for.digitv registration inaccordancegwithV-tle disclosure of the-above-citedpatentto Hchtet all4 The4 termination oifothis. KP signalfcausesthe; I-,2;.4, V'I',' and..` I0 leads.

A (Fig. 2) fromthe contacts oflthefchannelirelays to be-.cutthrough tothe sender.` The.originatf ingoperator. then operates key-set KSU) to.vp ulse out. the designationsofv` the destination. ofTv the call andrfollows.V these designations. by, a startsi'gnal which grounds the 1 andIU leads to indicate the completion offpulsing.

As disclosed in the. abovecited .patent to. Hecht.- et al., each digitistregistered the sender-by the` grounding of twofandv.,on1y two. ofthesve leads 0, I, 2,4;V 1 from the. multifrequencyr re.- ceivingcircuit, according to the typical two-out,-V oft-flve.- codelconvention:

Leads" .Y Grounded'.

If only one frequency is received 'bythesmultif frequency receiver;only' one 1 register relay will be operated and 'the-T012) relay-willnot. operate',` as described hereinafter, andthe sender: Willibeprevented from further functioning. Iff more than two frequencies:` arereceived-simultaneously by the multifrequency receiver, the 5R03 lead*to the sender is` grounded inthe multifrequencyPre'-,` ceiveras shownvinthe above-citedipatenttoI-Iecht' et al. Thisground is conducted overlead ROito the Windingu of relay OE( 3^) andto b'attery` Relay,-OE(3.)J,-in operating, locksto oif-norma'lrgroundi lead GDI through itsNo;` IL contact.andi-opens',V at itsNo. 3. contact; the`.J-'l.i.loop'to. thef. multi-` frequency receivertotprevent:v thefrec'eiptu` of Lanyfl further digits. Relay. OE 3f alsolinterrupts. the previouslytraced energizing circuit` fon relay RVI 3) atthe.No.:51contact'ofi'relay-OE(3)., and closes an energizing circuitfor.u relay RVI (31)'1 frombattery," windingof'relay R/I (3.),conductor.' 306, No. 4' contact.` ofA relay OE(3 conductorwl;interrupter INT(3), conductor3'08, conductor 30B; contact-ofV relaySBGI)` tor ground.' Sincerrelayf RV I (3-) is therebyperiodically!energized-and re" leased, reversed battery pulses are thussent overthe T andR-leadsrto the-originating: operator asi a recordersignali It may be notedV that anoperatingv circuiti prepared for' relay(IKA-(2) from conductor M I Whichmay begrounded in thernultifrequencyre- Registration of three-digit office codes In general, a three-digitoffice code is regi'stered on the A, B and C digit registers. Thenumerical digits designating the called station are registered on thethousands, hundreds, tens, units and stations digit registers,respectively.

When the called station is designated by a three-digit oiiice codefollowed by the numerical digits, receipt of two frequenciesrepresenting the rst or A oiice code digit causes the multifrequencyreceiver'iFig. 2) to ground lead H and two of the leads 0, I, 2, 4 and'I. However, in accordance with the conventional practice, the number lis never used for the first digit of an oilice code, and therefore thecombination of leads and I will never be grounded to represent the rstdigit of an office code. l f

The ground on two of the 0, I, 2, 4, and 'I leads operates thecorresponding register relays in the A digit register. For example, ifthe first digit of the ofiice code is 8, Yleads. I and 'I will begrounded by the multifrequency receiver. Ground will be conducted fromthe I lead. No. I4 contact of operated walking relay AA(2), conductorAI, winding of relay AI (6), and to battery. Relay AI (6), in operating,closes a circuit from ground, No. 3 contact of relay AHS), conductorAIA, winding of relay AIA(5) to battery. Relay AIA(6) is operated inorder to provide additional contacts for functions hereinafter to bedescribed. Simultaneous grounding of the I lead by the multifrequencyreceiver will pass ground over lead 1, No. 8 contact of relay AAH),conductor Ai', winding of register relay A1 (bi) to battery. RelayA'I(4), in operating, energizes, through its No. 4 contact, relay A1A(4)to provide auxiliary contacts. It is apparent that the grounding of anyother pair of leads Il, I, 2, 4, or 'I will result in the operation ofthe corresponding A and AA register relays.

It will be notedthat operation of register relays A2(6), A4(4), orA'I(4) will close a circuit from grounded conductor H, through the No. Icontact of any of those relays, conductor 205, conductor 206, No. 'Icontact of relay AA(2), conductor 201, winding of relay AB(2), to groundon o`normal ground lead GDS. Therefore, the operation of any pair of Aregister relays, except AIMS) and AHS) in combination, will provide apath for the H lead ground to shunt down the AB(2) relay, but continueto hold the AA(2) relay operated.

The holding windings of the two relays which have been operated in the Adigit register (any two except the combination of AIMS) and AI (5)) areconnected in parallel to the primary winding of 1'elay.TS(2). With theexemplary operation of the -A digit register relays AHS) and A'I(4), theholding winding of relay A! (6) is connected from batterytoconductor SBIthrough the No. 2 contact of relay AI (6), through the No. 2 contact ofrelay A'I(4), and then to conductor 40|. The holding winding of relayA'I (4) is also connected from battery through the No. 3 contact ofrelay A'II4)v and to conductor MI. The circuit then extends overconductor 40I, conductor 208, No. 4 contact of relay AA(2), conductor209, No. 3 contact of released relay ABQ), conductor 2 l0, conductor2I2, primary winding of relay 'I(2),` conductor 2 I 3, contact of relayCKA 2 to conductor K which is grounded in the multifrequency receivercircuit unless the latter has received more than two frequencies asabove discussed. As previously indicated, relay CKA(2) was released abrief interval following the receipt of thetwo frequencies by themultifrequency receiver, and at the same time the multifrequencyreceiver connected a ground on the J -L loop, which includes back(left-hand) contact of relay T0(2) as previously described, to lock thechannel relays of the multifrequency receiver operated after themultifrequency pulses from the originating keyset have ceased.

As previously mentioned, the T0(2) relay will not operate if only onefrequency is received in the multifrequency receiver. This is the casesince T0(2) is a marginal relay which will not operate in series tobattery when the resistance of the holding winding of a single registerrelay is in series therewith, but will operate when the resistances oftwo register relay holding windings in parallel are connected in seriestherewith.

When relay T8(2) operates, it locks over a path from battery, No. 6contact of relay ON3(2) conductor 284, conductor 2 I4 through thewinding of'relay T(2), front (right-hand) contact and armature of relayT0(2), through the No. 'I contact of relay ON 3(2) to ground in themultifrequency receiver. Relay TMZ), in operating, also opens, at itsback (left-hand) contact, the L lead to interrupt the locking path forthe channel relays in the multifrequency receiver.`

At this time, if the multifrequency pulses have ceased, or otherwisewhen the multifrequency pulses do cease, the channel relays willrelease. In so doing, they release an auxiliary check relay in themultifrequency receiver which removes the ground from the H lead andreconnects ground to the M lead. Removal of ground from the H leadreleases the AAG) relay inasmuch as the previously traced locking paththerefor is interrupted. The release of the AA(2) relay connects the t,l, 2, 4, and I leads over the Nos. I, 3, I3, II, and 9 contacts,respectively, of relay AA(2), through the Nos. 2, I4, I2, I0, and 8contacts, respectively, of previously operated relay BA(3) to thecorresponding relays in the B digit register. Relay AA(2), in releasing,also eectively transfers the H lead to the BA(3) relay over a pathincluding front contacts of the operated A2(6), A4(4), or 57(4) registerrelays, conductor 205, conductor 206, No. 6 con-v tact of relay AA(2),conductor 2I5, No. 'I contact of relay BA(3), conductor 309, winding ofVrelay BB(3), No. I contact of relay BB(3) to ground at off-normalground lead (3D3. Thus, in the B digit register, the H lead groundclosure does not depend on the prior operation of one `of the B digitregister relays, but is applied immediately to shunt down the BB(3)relay simultaneously with the operation of the Bdigit` in' the C`digitregister and so on through the' thousands, hundreds,

tens,y units, and stations digits.

Registration of two-digit office codes In general, a two-digit cnicecode is registeredon the' Avand B digit registers and thev C digit,

register is by-passed. As'before. the numerical digits designating thecalled station are resis-Y tered on the thousands, hundreds, tens,units, and stations digit registers, respectively. Any A digit exceptthe digit 1 may be used as a twodigit oflice code index. For whateverdigit or digits are selected to serve as indices for a twodigit officecode, the corresponding cross-connection terminals L2, L3, L4, L5, L6,L1, L8, or L9 at relay AB5 8 are connected to terminal TD at relayIIA'(2). For instance, if the digits 3 and 6 are to be the indices for atwo-digit oce code, terminals L3 and L6 at relay ABS 3 are connected toterminal TD at relay I IA(2).

In general, in order that receipt of a two-digit oice code index mayprepare the circuits so that the third digit to be received will beregistered in the thousands digit register rather than improperlyregistered in the C digit register, the circuits are arranged so thatregistration of a two-digit office code index on the A digit registerwill serve to release the CA(3) and CB(3) walking relays, therebyeffectively oy-passing the C' digit register. This is accomplished byassociating circuits with the A and AA digit register relays wherebyoperation of two of the ve relays in the A and in the AA digitregisters, representing a certain digit on a two-out-of-ve code basis,will result in ground being connected through the contacts of the AB5 8relay to the L terminal corresponding to that digit. The circuitsassociated with the ABEG!) relay are so arranged that that relay isinitially operated and remains operated if the A digit is to 4, but isreleased if the A digit is to 9. Ground will therefore vbe connected toterminal TD if the initial digit is the index, or one of the indices,for a two-digit station code. Ground on the TD terminal will beconducted through a back contact of the IIA(2) relay to the TD(3) relaywhich serves to release the CA(3) and CB(3) Walking relays therebyeiectively ley-passing the C digit register and causing thethirdreceived digit to be registered in the thousands digit register asit properly should be.

In detail, relay AB5(8) Was initially operated upon the operation ofrelay ONI (2) over an energizing circuit which may be traced from groundon olf-normal ground lead GDI, conductor 462, No. Contact of relayA404), conductor 433, No. contact of relay A'I'(4), conductor 404,conductor 685, winding of relay AB5(8), to battery. When the digits "2or "3 are registered, neither relay A503) nor relay A'I('4) is operatedso this energizing path is uninterrupted and relay AB-5(3) will remainoperated and terminals L2 and L3 will be connected through the Nos. 3and 9 contacts, respectively, of relay AB5(8). When the digit 4 isregistered, relay A403) will operate but an energizing path for relayAB5(8) may still be traced from ground on olf-normal ground lead GDI,conductor 402, No. 5 contact of energized relay A4(4), conductor Et, No.t Contact of relay A2(6), conductor 603, No. I contact of relay AHS),conductor 6&2, conductor G35, winding of relay ABEG?) to battery.Therefore terminal L4 will be connected through the No. 1 contact ofrelay AB5(8). If any larger digit, "5 through "9, is received, theenergizing path for relay AB5(8) will be interrupted at one or more ofthe following points: No. 4 Contact of relay AH), No. 6 contact of relayA26), No. 5 contact of relay A4(4), No. B contact of relay AHt).Therefore, when a digit from "5 to "9 is registered in the A digitregister, relay ABEG!) will release .so that terminals L5, L6, L'I, L8and L9 Will be connected through the Nos. I, 4, 2, IIJ, and 8 contacts,respectively, of relay AB5(8).

Presuming now that the digits 3 and 6 have been selected as the indicesfor a two-digit office code andv that the L3 and L6 terminals (Fig. 8)have been cross-connected to the TD terminal (Fig. 2). An initiallyreceived digit 3 Will then be registered in the A and AA digit registersas above described with the AI (6), A2(6), AIA(B), and A2A(4) relaysbeing operated and locked. The AB5 relay will remain operated aspreviously discussed. Ground Will therefore be conducted from off-normalground lead GDI, conductor 405, No. 4 contact of operated relay A2A(4),conductor 406, conductor 4.0?, No. 2 contact of operated relay AIA(6),conductor 606, No. II! Contact of relay BTR(8), conductor No. 9 contactof operated relay AB5(8) to terminal L3 which is connected to terminalTD. Similarly, receipt of the A digit 6, which also has been selected asa two-digit ofiice code index, will result in the operation of registerrelays A2 (6) A4(4) A2A(4) and A4A(4). Relay AB5(8) will be released asabove discussed. Ground will be conducted from off-normal ground leadGDI, conductor 408, No. I contact of operated relay A2A(4), conductor409, No. 2 contact of operated relay A4A(4), conductor 4I0, No. Icontact of relay BTR(8), conductor 802, No. 4 contact of released relayAB5(B), to terminal L6 which is connected to terminal TD.

Ground at terminal TD is passed over the No. 2 contact of relayv IIA,(2), conductor 24|, Winding of relay TD(3), to battery. Relay TD(3)operates and locks over its No. 6 contact to ground on off-normal groundlead GDI. As will be recalled from the previous discussion, both theoperating and locking paths for relays CA(3) and CB(3) included the No.9 contact of relay TD(3). Therefore, the operation ofrelay TD(3) willvcause therelease of relays CA(3) and CB(3). The release of these relaystransfers the 0, I, 2, 4, and 'I leads to the Walking relays associatedwith the thousands digit register as previously described so that thethird digit to be received is properly channeled to the thousands digitregister.

It may be noted that the AB5(8) relay should be of the fast-releasingtype so that it will be released, if it is going to release, before theoperating ground for the TD(3) relay is supplied by the operation oftheauxiliary A digit register relays AOA(6) to AIA(4).

Special codes Two types of special codes may be employed in connectionWith intertoll dialing: service codes and TX codes.

Service codes are those used by toll operators to obtain specialconnections, such as to the toll information board, to the toll testboard, to route and directory positions, and so forth. Service codesgenerally are, and are herein presumed to be, two-digit numbers prexedbythe digit 1." As indicated hereinafter, a TX code is prefixed by thedigits 11, and therefore the rst digit of the service code proper cannotbe the digit 1." Therefore a service code, when prefixed by the digit 1,may be any number from to 109, and from 120 to 199.

TX codes may be either two-digit or three-digit codes prefixed by thedigits 11, i. e., llEX or llEXX codes, where X represents any digit from0 to 9, and E represents any digit except 0.

TX codes are used principally in the completion of delayed toll calls.In the case, for instance, of a person-to-person call in which thecalled party is unavailable, the operator may ask that the called partybe requested to call the toll or long distance operator at the citywhere the call has originated, and designates this operator by the cityname and a number, two-digit or three-digit as the case may be. When thecalled party later asks his own operator to connect him with the tolloperator EX or EXX in the distant city, his operator will dial or keythe digits llEX or llEXX over a toll line. This will connect the tollline to the operator position or team in the originating office, whowill then complete the call to the original calling subscriber.

Certain TX codes are used for special purposes such as establishing tollconference connections, connections to charge-quotation operators, andso on.

Registration of service codes When a service code, 100 to 109, or 120 to199, is received, the initial 1 is registered by the operation of thecounting relays IIA(2) and IIA(2), and the second and third digits areregistered on the A and B digit registers.

When an initial digit 1 is received, which indicates that the ensuingdesignation is not an oilice code, it is received and passed into the Adigit register in the normal fashion. Relays A0(6), AHB), AOA(6) andAIA(6) are operated to register the digit, but it may be noted thatthese relays do not lock operated. As previously indicated, theoperation of the combination of register relays A0(6) and AHB) does notestablish a path whereby the H lead ground may shunt down the AB(2)relay to advance the walking circuit. Instead, the operation of thiscombination of A digit register relays closes a circuit from ground onolf-normal ground lead GDI, conductor 601, No. I contact of relay AI (6)conductor 608, No. 2 contact of relay A0(6), conductor 609, No. 3contact of relay IIA'(2), conductor 2I6, winding of relay IIA(2), tobattery. It may be noted that although relay IIA(2), in operating,prepares an energizing path for relay IIA(2) over a path from battery,winding of relay IIA(2), conductor 2| 6, Winding of relay IIA(2),conductor 2I9, No. 2 contact of relay IIA(2), conductor 220 to ground onoff-normal ground lead GDI, relay IIA(2) will not operate at this timesince that energizing path is shunted to ground over the tracedenergizing circuit for relay IIA 2). Upon the operation of relay IIA(2),battery is connected through resistance Y(2), which is equivalent to theresistance of two register relay locking windings in parallel, No. Icontact of relay IIA(2), conductor 2I'I, No. 6 contact of relay IIA(2),conductor 2I8, No. I contact of register relay A0(6), conductor 6I0,conductor 2 I2, winding of relay T0(2), conductor 2I3, contact of relayCKA(2), to conductor K which is grounded in the multifrequency receiver.Operation of relay T0(2) allows the channel relays in the multifrequencyreceiver to release as previously described and the release of theserelays in turn releases the digit register relays AMS), AHB), AOA(6),and AIA(6). lease of register relay A0 (E) interrupts the above- ,tracedenergizing path for relay T0(2), and consequently relay T0 2 releases.The release of relays A0(6) and AI(6) also interrupts the previouslytraced shunting path around relay Re- F IIA'(2), and relay IIA(2) willbe operated. The initial digit 1 is therefore registered by theoperation of relays IIA(2) and IIA(2).

The rst digit of a service code (the second digit to be received) may beany digit except the digit 1 and since the A digit register walkingrelays have not been released, the register circuits of the senderrespond to the receipt of the first and subsequent digits of the servicecode proper in the same manner as they respond to the first andsubsequent digits of an office code, i. e., the first digit of theservice code proper is registered on the A digit register, the A digitregister walking relays are released, and the second digit of theservice code is registered on the B digit register.

Registration of TX codes When a TX code preceded by the digits 11 isreceived, the two successive digits 1 are registered on the IIA(2),IIA'(2), IIB(2), and IIB'(2) counting relays. The following two or threedigits of the TX code are registered on the A and B, or on the A, B andC digit registers, respectively.

The initial digit l preceding a TX code is registered on the IIA(2) andIIA(2) relays as described above in connection with the initial digit lof a service code. Receipt of the second digit 1 preceding a 'IX coderesults in the reoperation of A digit register relays A0(6) and AI(6) inthe same manner. These register relays, in operating, close a circuitfrom ground at oli-normal ground lead GDI, conductor 601, No. I contactof relay AI (6), conductor 608, No. 2 contact of relay A0(6), conductor609, No. I contact of relay IIA(2), conductor 22|, No. 5 contact ofrelay IIB(2), conductor 222, conductor 223, winding of relay IIB(2) tobattery. Relay IIB(2), in operating, prepares an energizing circuit forrelay IIB'(2) from ground on off-normal ground lead GDI, conductor 226,No. 2 contact of relay I IB(2), conductor 225, winding of relay IIB(2),conductor 224, conductor 223, winding of relay IIB(2) to battery, butrelay I IB(2) cannot operate at this time because of the shuntcomprising conductor 222 and the path to ground through the contacts ofregister relays A0(6) and AI(6) traced in describing the energizingcircuit for relay I IB(2) When relay IIB(2) operates, relay T0(2) isagain energized through a path from battery. resistance Y(2), conductor221, No. I contact of relay IIB(2), conductor 228, No. 9 contact ofrelay IIB(2), conductor 229, conductor 2I8, No. I contact of relayA0(6), conductor 6I0, conductor 2I2, winding of relay T0(2), conductor2I3, contact of relay CKA(2), and conductor K to ground in themultifrequency receiver. Operation of relay T0(2) allows the channelrelays in the multifrequency receiver to release, and they, in turn,release register relays A0(6) and AHS). Relay T0(2) will then releasesince its energizing circuit will be interrupted at the No. I contact ofrelay AMB). The register relays, in releasing, will also interrupt, atthe No. 2 contact of relay A0(6) and at the No. I contact of relay AKG),the previously traced shunting circuit around the winding of relay IIB'(2), and therefore relay IIB(2) will operate.

Relay IIB(2), in operating, prepares a path to close the H lead to shuntout relay AB(2) and to provide a locking path for relay AA(2) on thenext operation of the relays in the A digit register, over a path fromthe H lead, No. I contact of relay I lIB'(2) conductor 230, conductor206, No. 1 contact of relay AA(2), then in one direction through theWinding of relay AA(2) to battery and in the other direction throughconductor 201, winding of relay AB(2) to ground at olinormal ground leadGDB. 'I'rhis path is rendered elective upon the operation of anycombination of two A digit register relays, including relays A(6) and AI(I3), operative to register the digit 1. Therefore, the third digit tobe received (the rst digit of the TX code) will be registered in the Adigit register. This is true even if the third digit is l since relayIIB(2), in operating, prepares an independent locking path for theholding windings of relays A0(B) and AI(6) from battery, holding windingof relay A0(6), No. 3 contact of relay A0(6) to conductor BIH and frombattery, holding winding of relay AI (6), No. 2 contact of relay AI (S)to conductor 50|, conductor 6I I, No. I0 contact of relay lIB(2),conductor 23S, conductor 208 No. l contact of relay AA(2), conductor209, No. 3 contact of released relay AB(2), conductor 2I0, conductor2I2, winding of relay T0(2), conductor 2 I3, contact of relay `CKA(2) toconductor K which is grounded in the multifrequency receiver. Theregistration then proceeds in the normal fashion with the AA(2) relayreleasing to prepare the B digit register to register the fourth digitto be received (the second TX code digit). 1f threedigit TX codes areused the third digit thereof (the fth digit to be received) isregistered on the C digit register.

Communication with marker--three-digit o'ice codes After suiiicientinformation has been registered in the sender, the sender seizes amarker which may be of the general type shown in Patent 2,235,803,granted March 18, 1941, to W. W. Carpenter and preferably is of a typeembodying the modications disclosed in Patent 2,559,312, granted July 3,1951 to J. B. Newsom.

In the case of a three-digit omce code, the sender is arranged to seizea marker after the three oince code digits have been registered, Withtwo of the live C digit register relays 00(1) to 01(5) operated, acircuit is closed from battery, holding windings of the two operatedrelays 00(1) to 01(5), No. I contact of those operated C digit registerrelays, conductor I, No. 5 contact of released walking relay CA(3),conductor 3|0, No. 3 contact of unoperated relay TD(3), conductor SI I,winding of relay CL(3) to ground at oir-normal ground lead GDI. RelayCL(3), in operating, closes a circuit from oli-normal ground lead GDI,conductor 3I2, No. I contact of relay CL(3), conductor SIS, No. Iicontact of relay OE(3), conductor 3I4, Winding of relay DST(3) tobattery. Relay DST(3) locks to .ground on ofi-normal ground lead GDIover its No. I contact and closes, at its No. 2 contact, a circuit fromground on OIT-normal ground lead GDI, conductor 3I5, conductor 23|,winding of relay BTR(8) to battery, thereby operating relay BTR(8). Theoperation of relay DST(3) also closes circuits (not shown) to cause themarker vconnector (Fig. 8) to connect the leads from the sender registerrelays into the marker (Fig. 8).

The sender transmits the oice code registrations to the marker B-, D-,and G- series leads which are shown connected to the marker ccnnector inFig. 8. Any pair of A and AA register relays operated to register the Adigit connects ground to one of the B0 to B4 leads to the .14 marker.For example, registration of the digits 0 or 5 will ground the B0 lead,over a circuit. for the digit 0," from ground at lead GDI, No. I contactof relay A4A(4), conductor 4I3, No. I contact of relay A1A(-4),conductor 4I4, conductor GI I, No. 4 contact of operated relay BTR(8),

conductor 803, No. I contact of unoperatedrelay TXA(8) to lead B0.Registration of the digit 5 results in the closure of a, circuit fromground at oir-normal ground lead GDI, No. I .contact of relay A4A(4),conductor 4I2, No. I contact of relay AIA(6`), over conductor 6I I, No.4 contact of operated relay BTR(8), conductor 803, No. I contact ofunoperated relay TXA(8), and to lead B0. Similarly, and by obviouscircuits, registration of the digits 1 or 6 in the A digit registerresults in the grounding of lead BI, registration of the digit 2 or 7results .in the grounding of lead B2, registration of the digit "3 or 8results in the grounding of lead B3, and registration of the digit 4 or"9 results in the grounding of lead B4. Since the grounding of one ofthe B series leads indicates only that one of two digits is registeredin the A .digit register, means must be provided to enable the marker todistinguish between the pairs of digits. This is `accomplished bygrounding the BB5 lead if the digit is less than 5 and by grounding theBA5 lead if the digit is 5 or above. As previously discussed, relayAB5(8) is responsive to the value of the digit registered in .the Adigit register, being held operated if the digit is less than 5 andbeing released if the digit is 5 or greater. With a digit less than 5registered and relay AB5(8) consequently being operated, ground isconnected over the No. 5 contact of relay AB5(8), conductor 804, No. I2contact of relay TXA(B), to the BBE lead. With a digit 5 or greaterregistered and relay AB5(8) consequently released, ground isconnectedover the No. '0 contact of relay AB5(8), conductor 805, No. I 0contact of relay TXA(8) to the BA5 lead.

Similarly, for digits 0 to 4 registered on the B digit register, one ofthe leads DI] to D4 is grounded by the operated B register relays andlead DB5 is grounded through the No. 2 contact of operated relay BB5(0).For digits 5 to 9 registered on the B digit register, one of the leadsD0 to D4 is grounded by the operated B register relays and lead DAS isgrounded through the No. I contact of released relay BB5(9).

.In the case of the C digit register, one of the G0 to G4 leads isgrounded by the operated register relays, but the 0B5 relay,corresponding to the AB5 and BB5 relays, has been omitted to demonstratethat Wtih sufficient contacts available on the register relays, theabove 5 or be low 5 function may be executed in the register relaysthemselves. The No. 5 make contact of relay 00(1), the No. 3 makecontact of relay 0I(1), the No. 3 make contact of relay 02(1), the No. 2make and the Nos. S and 1 transfer contacts of relay 04(5), and the No.2 make and the Nos. 'I and 8 transfer contacts of relay 01(5) aresuitably interconnected by obvious circuits to accomplish this function.Thus, the operation of relays 04(5) and 01(5) for the digit 0, theoperation of relays 00(5) and 0I (5) for the digit l, the operation ofrelays 00(5) and 02(5) for the digit 2, the operation of relays CI (5)and 02(5) for the digit 3 (with both relays 04(5) and 01(5) unoperated),or the operation of relays 00(5) and 04(5) for the digit 4 will serve toground lead GBS to indicate a digit less than 5. On the other hand, theoperation of relays 02(5) and 04(5) for the digit 6, the operation ofrelays (5) and C1( 5) for the digit 7, or relays CI (5) and 01(5) forthe digit 8, or relays 02(5) and 01(5) for the digit 9 (with relay 04(5)unoperated) will serve to ground lead GA to indicate a digit 5 orgreater has been registered.

The LA lead, which is connected to the marker through the markerconnector, is grounded at the No. 1 contact of relay IIB'(2), as is alsothe case in two-digit oflice codes and service codes, to serve, in themarker, to control the points of termination of the DA5 and DB5 leads.

Communication with, markeT-two-dz'git olice codes In the case of atwo-digit ofIice code, the sender is arranged to seize a marker afterthe two ofce code digits have been registered. It will be recalled thatwhen a two-digit office code index is received and registered in the Adigit register, relay TD(3) is operated. Then, with two of the ve Bdigit register relays B0(1) to B1(5) operated, a circuit is closed frombattery, holding windings of the two operated relays B0(1) to B1(5), No.I contacts of those operated B digit register relays, conductor 102, No.5 contact of released walking relay BA(3), conductor 3 I 6, No. 4contact of operated relay TD(3), conductor 3I I, winding of relay 0L(3)to ground at off-normal ground lead GDI. As in the case of three-digitoce codes, relay CL(3) operates relay DST(3) which serves to operaterelay BTR(8) and to cause the marker connector to connect the leads fromthe sender register relays into the marker.

Due to the character of the marker, it is desirable to transmit thetwo-digit oice code to the marker in the form of a three-digit code with0 as the second digit. In other words, a two-digit code such as istransmitted as code 205 to the marker.

This is accomplished by transmitting the information contained in the Adigit register by grounding leads of the series B0 to B5 and BA5 or BB5in the same manner as in the case of three-digit office codes, bygrounding leads D0 and DB5 as if zero had been registered on the B digitregister, and by transferring the contacts of the B digit register fromthe marker D series leads to the marker G series leads so that the digitregistered on the B digit register is transmitted to the marker as if ithad been registered in the 0 digit register.

The grounding of the D0 and DB5 leads, representing the digit 0, occursas a result of the operation of relay TD(3) over a path from ground,Nos. I and 2 contacts of operated relay TD(3), conductors 3I8 and 3| 9to leads D0 and DB5, respectively, to the marker connector and marker(Fig. 8).

The operation of the TD(3) relay, when a twodigit ofce code index isreceived, also closes a circuit from ground, No. 1 contact of relayTD(3), conductor SI1 to the windings of relays TXB(9) and TXO 9 and tobattery. Leads 906, 901, 908, 909 and 9I0 from the contacts of the 0digit register relays are disconnected from the G0, GI, G2,.G3 and G4leads, respectively, upon the operation of relay TXC(9). Operation ofrelay TXB(9) results in the transfer of the B digit register leads 90|,902, 903, 904 and 905 from the D0, DI D2, D3 and D4 leads, respectively,to the G0, GI, G2y G3 and G4 leads, respectively. Operation of relaysTXO(9) and TXB(9) also disconnects the GA5 and GB5 leads from the 0digit register, and connects these leads to the No. I and No. 2contacts, respectively, of the BB5 relay whereby lead GA5 or lead GB5will be grounded, responsive to the condition of relay BB5, depending onwhether the digit registered in the B digit register is above or belowthe digit 5. Thus, in the case of a two-digit oice code, the digitregistered in the B digit register will be transmitted to the markerover leads normally associated with the C digit register.

Communication with. markerservice codes In the case of service codes andtwo-digit TX codes, relay DST(3) is operated by relay ST(3), which, inturn, is operated upon the receipt of the start signal which theoriginating operator transmits following the service or TX code. Aspreviously indicated, this start signal comprises a combination offrequencies that results in the grounding of the I and I0 leads by themultifrequency pulse receiving circuit (Fig. 2).

It will be recalled that when a service code preixed by the digit 1 isreceived, the initial digit l is registered on the I IA(2) and IIA(2)relays, the second digit to be received (the rst digit of the servicecode) is registered on the A digit register, and the third digit to bereceived (the second digit of the service code) is registered on the Bdigit register. With the initial digit l and the two digits of theservice code registered, receipt of the start signal serves to operaterelay 01(5) over grounded conductor 1 through the No, 9 contacts ofreleased relays AA(2) and BA(3), No. 8 contact of operated relay 0A(3),conductor 320, winding of relay 01(5) to battery. Receipt of the startsignal also grounds the No. I0 lead which operates relay ST(3) over apath from grounded conductor I0, No. 2 contact of unoperated relay0L(3), conductor 32|, No. 1 contact of operated relay IIA(2), No. 4contact of unoperated relay I IB (2) (or by-passing this contact if theS option is used as hereinafter explained), conductor 240, No. 8 contactof unoperated relay 02(1), conductor 103, No. 3 contact of relay 01(5)(which is operated by the start signal), conductor 50|, winding of relayST(3), to battery. Relay ST(3), in operating, closes a circuit fromground at off-normal ground lead GDI, No. 3 contact of relay ST( 3),conductor 322, No. 5 contact of relay OE(3), conductor 3I4, winding ofrelay DST(3) to battery. Relay DST(3) in operating, operates relayBTR(8) and causes the marker connector to connect the leads from thesender register relays into the marker as previously described. RelayDST(3) also prepares an operating path for the energization of relaysTXA(8), TXB(9), and TXO(9), as hereinafter described.

In transmitting the service code designation to the marker, the initialdigit l is transmitted over the B series leads normally associated withthe A digit register, the next digit, which is registered in the A digitregister, is transmitted over the D series leads normally associatedwith the B digit register, and the last digit of the service code, whichis registered on the B digit register, is transmitted over the G seriesleads normally associated with the 0 digit register.

The initial digit l is transmitted to the marker by the grounding of theBI and BBS leads upon the operation of relays I IA(2) and IIA' (2).These paths may be traced from ground, No. I contact of operated relayII A(2), conductor 232, No. 3 contact of relay I IB(2) (or by-passingthis I7' contact under the S option) ,y conductor 233, to the BI lead;and from ground, No. contact of operated relay HA'(2), conductor 234,No. 8 contact of relay IIB(2) (or by-passing this contact under the Soption), conductor 235, to lead BBS.

The operation of relays IIA(2) and lIA(2) to register the initial digitl also results in the operation of relays TXA(8), TXB(B), and TXC(9)over paths from ground at off-normal ground lead GDI, No. 2 contact ofrelay DST(3), conductor SI5, conductor 236, No. 3 contact of relayIIA(2), conductor 231, No. 2 contact of relay IIB(2) (or by-passing thiscontact under the S option) and then over the parallel paths ofconductor 243, winding of relay TXA(8) to battery, and conductor 239,No. 8 contact of relay TD(3), conductor 3 Il, windings of relays TXB(9)and TXC(9) to battery. The operation of relay TXA(8) transfers the leadsfrom the A digit register relays to the D series leads and connects theMill and SL35 leads from the AB5(8) relay to the DA5 and DB5 leads. Theoperation of relay TXB(9) transfers the leads from the B digit registerrelays to the G series leads and connects conductor 9| I, from the No. 2contact of relay BB5(9), to conductor G35. Relay TXC(9), in operating,connects conductor SH2, from the No. I contact of relay BB5(3), toconductor GAE and also disconnects the leads from the C digit registerrelays from the G series leads.

Communication with marker-TX codes As will be explained in more detailhereinafter, in the case of two-digit TX codes the functioning of thecircuits is similar and the resulting transmission to the marker is thesame as in two-digit service codes. In the case of three-digit TX codes,the operation and resulting transmission to the marker is the same as inthree-digit oce codes. Therefore, means must be provided to enable themarker to distinguish TX codes from other types of codes. This isaccomplished upon the operation of relay IIB(2) when the second digit lprei'lxing a TX code is received. Relay I |B(2), in operating, breaks,at its No. l Contact, the previously existing connection between groundand lead LA, and establishes, at its No. 5 contact, a connection. fromground to lead EA. Ground on lead LA indicates to the marker that anoffice or service code is being transmitted from the sender, and groundon lead EA indicates thatv a TX code is being transmitted.

Although the use of either two-digit or threedigit TX codes iscontemplated, it may be noted that in the present disclosure noprovision is made for the combined use of these two types of TX codes.When three-digit TX codes are used, the T option wiring at relay I IB(2)is used, and when two-digit TX codes are used, the S option wiring isused. It may be noted that the S option wiring comprises the placing ofshunts around the circuits through the Nos. 2, 3, 4 and 8 contacts ofrelay IIB(2). Since relay IIB(2) is unoperated except in theregistration of TX codes, whether "5 or T option Wiring is used isimmaterial in the registration of oice or service codes. For two-digitTX codes, the use of the S option shunts at relay IIB(2) renders thecircuits operative in the same fashion as that described for servicecodes. Since the Nos. 2, 3, 4 and 8 contacts of relay I|B(2) areshunted, the operation of relay IIB(2) is ineffective to break thecircuits through these contacts, ground is placed on the BI and BB5leads and relays TXA(8), TXB(9), and TXC(9) are operated as beforedescribed. Therefore, the digit 1 is transmitted over the B seriesleads, the rst digit of the TX code proper, which is registered on the Adigit register, is transmitted over the B series leads, and the seconddigit of the TX code proper, which is registered on the B digitregister, is transmitted over the G series leads.

For three-digit TX codes, T option wiring is used at the I IB'(2) relay.Therefore, with relay HB(2) operated, the previously traced energizingcircuits for relays TXA(8) TXB(9) and TXC(9) are interrupted at the No.2 contact of relay l IB (2) Thus the leads from the A, B, and C kdigitregisters are connected to the marker B series, D series and G seriesleads, respectively, in the same fashion as for regular office codes,and thus a three-digit TX code is transmitted to the marker in the samemanner as is a threedigit oiiice code. The above-discussed grounding ofthe EA lead again serves as a means for the marker to distinguish TXcodes from oice or service codes.

After the sender has seized a marker and has transmitted to the markerthe above-discussed and other information, the marker decodes thisinformation and passes information back to the sender by means of whichthe sender may make its selections in either a toll office, callindicator ofce, cross bar ofce, panel oiice, or step-by-step office. Themarker also seizes ofce and trunk link frame connectors and establishesconnection therewith over cables of conductors OLC and TLC. (Fig. 1).The marker then, by circuits not shown, grounds lead DC through thesender link (Fig. l), to the trunk circuit of Fig. 1, through the No. dcontact of relay DI (I), conductor I D9, winding of relay FU), tobattery. Relay F(|f), in operating, performs several functions includingthe closing of the sleeve to the SL lead to the marker for testingcontinuity, and the extending of the ground on the DC lead through theNo. 4 contact of relay F(|) to the LC lead to operate a link connectorrelay associated with a primary switch in the trunk link. The marker,after checking the condition of the switches, releases relay F(I). Themarker then checks that the sleeve ground from the No. 4 contact ofrelay T(i) is capable of holding the connection, andr then releases.

When the sender has completed its selections, lead D (Fig. 1) is.grounded in a portion of the sender not shown. This ground is conductedIover lead D, No. 8 Contact of released relay F( I conductor III),conductor Il I, winding of relay D( l) to battery. Relay D( I) inoperating, closes a circuit from ground, No. 3 contact of relay D(I),conductor H2, Winding of relay Dl (I), to battery. Relay DI(.I), inoperating, interrupts the energizing path for relay A(I from the ringconductor R at the No. 8 contact of relay DI (I),

and prepares an energizing circuit for relay A( I) from the tipconductor of the trunk TR, upper contacts of test jack JA(I tipconductor T, conductor H3, No. 'I contact of relay DI( I), conductor It2, No. l contact of relay T(|) (when relay T(I) subsequently releases),conductor H03, conductor |04, lower winding of relay A( I) to ground.Thus the connections from the incorning trunk to relay A(l) have beenreversed by the operation of relay DI (I). Operation of relay DI(|) alsocloses a groundV through the No. 3 contact of relay D2(I), conductor I I4, No. 3 contact of relay TU), conductor |15, No. 5 contact of relay DI(I), to conductor DC to the sender. Relay DI(I), in operating, alsocloses a temporary holding circuit for the trunk link and connectorswitches.

Upon receiving ground on lead DC, the sender, as previously explained,removes ground from lead CO which interrupts the energizing circuit forrelay T(I). Relay T(I) releases and closes the previously tracedenergizing circuit for relay A(I) from battery on the tip conductor T.Release of relay T( I) also removes ground from the DC lead at the No. 3contact of relay T( I), and also closes an energizing circuit for relayD2(I) from ground, No. 5 contact of relay T(I), conductor |08, No. 9contact of relay DI(I), conductor IIS, Winding of relay D2(I), tobattery. Relay D2( I) locks operated under the control of relay DI(I)through a path from ground, No. 4 contact of relay D2( I), conductor|08, No. 9 contact of relay DI(I), conductor IIS, winding of relayD2(I), to battery. Relay D2(I), in operating, closes the iinal holdingcircuit for the trunk and ofce switches and opens lead ST at theNo. 'Icontact of relay D2(I).

When trunk closure takes place, relay A(I) operates and connects groundthrough its contact to conductor |05. This ground is conducted throughthe No. I contact of relay DH), serves as a locking ground for relayD(I), and is conducted over conductor IH, conductor IIU, No. 8 contactof relay FU), to the D lead to serve as a disconnect signal to thesender. The sender link releases and leaves the connection under controlof relays A(I) and D(I) When the called subscriber answers, the incomingtrunk in the called oiiice reverses its battery and ground to the tandemtrunk circuit of Fig. 1. This reversal results in the operation of relayCSU). 'Ihe CSU) relay closes a circuit from ground, armature of relayCS( I No. I contact of relay CSU), conductor II'I, No. 2 contact ofrelay D2(I), winding of relay T(I), to battery. Relay T( I) inoperating, reverses the battery and ground to the calling oice, aspreviously described, thereby repeating the supervision.

When the call has been completed and the calling subscriber hasdisconnected, the originating operator opens the trunk circuit at theoriginating oiiice and relay A(I) releases. Release of relay A(I)interrupts the holding path for relay D( I), and relay D(I) alsoreleases. Relay D(I) interrupts the energizing circuit for relay Di (I)and relay DI(I) releases. Relay DI(I), in releasing, interrupts thepreviously traced holding path for relay D2(I), so relay D2(I) releases.Relay D2(!), in releasing, releases the trunk link and connectorswitches and recloses, at its No. I contact, lead ST in preparation forthe receipt of the next call.

The above description of the invention is purely illustrative and theassociation of the invention with the disclosed cooperating equipment isbut representative, and is not to be interpreted in a limiting sense.

What is claimed is:

1. In a telephone system, a plurality of registers for registering thedigits of telephonie designations, a like plurality of pairs of relays,circuit means connected to said pairs of relays simultaneously operatingall of said relays, circuit means comprising selective control means andcontacts of a iirst of said pairs of relays connecting said controlmeans toa first of said registers for operating said rst register inaccordance with the first digit of a designation, relay means connectedto said rst register and to said first pair of relays rendered effectiveby the registration of any of certain digits on said first register torelease said first pair of relays, circuit means comprising saidselective control means and contacts of said iirst pair and of a secondpair of said relays connecting said control means t0 a second of saidregisters for operating said second register in accordance with thesecond digit of a designation, relay means connected to said secondregister and to said second pair of relays rendered eiective by theregistration of a digit of any value on said second register to releasesaid second pair of relays, circuit means comprising said selectivecontrol means and contacts of said rst and said second and of a thirdpair of said relays connecting said control means to a third of saidregisters for operating said third register in accordance with the thirddigit of a designation, and relay means connected to said first registerand to said third pair of relays rendered effective by the registrationo1 a digit of a predetermined particular value on said first register torelease said third pair of relays.

2. In a telephone system, a iirst, a second and a third register iorregistering digits of telephonie designations, a rst, a second and athird group of output conductors, register control means, circuit meansfor successively connecting said registers to said Control meansrforsetting said registers in accordance with the digits of a telephonicdesignation, apparatus including said first register connected to saidcircuit means eilective when said rst register is operated to apredetermined setting for disabling said circuit means to connect saidthird register to said control means, relay means for connecting saidrst, said second and said third groups of conductors to said iirst, saidsecond and said third registers respectively, means including said relaymeans connected to and controlled by said apparatus for connecting saidthird group of conductors to said second register, and means includingsaid relay inea-ns connected to and controlled by said apparatus forconnecting a source of potential to a preselected one of said secondgroup of conductors.

3. In a telephone system, a iirst, a second and a third register forregistering digits of telephonic designations, a rst, a second and athird group of output conductors, register control means, circuit meansconnecting said iirst register to said control means for setting saidiirst register in accordance with the first digit of a designation,means including said circuit means connecting said second register tosaid control means for setting said second register in accordance withthe second digit of a designation, apparatus including said rst registerconnected to said circuit means effective when said iirst register isoperated to a predetermined setting for disabling said circuit means toconnect said third register to said control means, relay means forconnecting said rst, said second and said third group of conductors tosaid first, said second and said third registers respectively, meansincluding said relay means connected to and controlled by said apparatusfor connecting said third group of conductors to said second register,and means including said relay means connected to and controlled by saidapparatus for connecting a source of potential to a preselected one ofsaid second group of conductors.

4. In a telephone system, a rst, a second and a third register forregistering the digits of telephonic designations, a rst, a second and athird 211i group of.' output conductors register control means, circuitmeans connectinggsaidifirst regis,-A ter to said control means. forksettingsaid: iii-rst register in accordance With the first, digit of' adesignation, apparatus including said. firstregis-i ter connected tosaidcircuit' means effective when said first register is operated to apredetermined setting for releasing said rstregister, relay means forconnecting saidfirst, said second andv said third' group of' conductorsto. said iirst, said second and' said third registers respectively,means including said relay means connected to and controlled by saidapparatusfor connecting a source of potential to apreselected one ofsaid firstl group of conductors, means including said relay meansconnected to and controlledV by said apparatus for connecting saidsecond group of conductors to saidnrst register, and means includingsaid relay means connected to and controlled by said apparatus forconnecting said'third group-of conductors to said Second register.

5. In a telephoneV system, a rst, a second anda third register forregistering the digits of telephonic designations, a first, a second andathird group of output conductors; register; control means, circuitmeans connecting said rst register to said control means` for settingsaid iirst register in accordance with the first digit of a designation,means including said circuit means and said first register forconnecting saidsecond register to said control means for setting saidsecond register in accordance With the second digit of a designation,apparatus including said first register connected to said circuit meanseffective when said rst register is operated to a predetermined settingfor releasing saidfirst register, relay means for connecting said first,said second and said third group oi' conductors to said rst, said secondand said third registers respectively, means including said relay meansconnected to and controlled by said apparatus for connectinga sourceI ofpotential to;l a preselected one of saidfirst group of conductors, meansincluding said circuit means and said second register forv connectingsaid third register to said control means for setting said thirdregister' in accordance with the third-digit of a designation, meansincluding said relay meansA connected to and controlled bysaid apparatusfor connecting said second group of conductorsto said rst register, andmeansincluding'saidrelay means connected to and controlled by saidapparatus for connecting said third group of conductors to said secondregister.

6. In a telephone system, a code transmitting device for transmittingthe digits of telephonie designations, a plurality of registers forregistering said digits, a group of input conductors connected to saiddevice, circuit means connecting the first of said registers to saidinput conductors for setting said first register in accordance with thefirst digit of a designation, means including said circuit means andsaid first register eiiective when said first register is operated toany of its setting except certain settings for connecting the second ofsaid registers to said input conductors for setting said second registerin accordance With the second digit of a designation, and apparatusconnected to said first register effective when said rst register isoperated to said certain settings for releasing said rst register.

'7. In a telephone system, a code transmitting device for transmittingthe digits of telephonie designations, a rst, a second and a thirdregister forfregistcrinasaid; digits, a group.; of. input. con`ductorszconnactedto..said dcvicaarst, a second and: a third; group of;output: conductors, circuit means;connectingfsaidirst register tosaidinput Conductors.: for; settingr Said first register in acconfiancewith the rst digitl of a designation, means includingsaid circuitmeansand said first registeiteffective. when said first register issetto anyfof itssettingsexcept certain settings for connectingsaidjsecondregister to said input conductors for setting said second register inaccordancewith the second digit of a designation, apparatusincludingsaid first register connected to said circuit means eiective when saidiirst register is operated to said certain settings for releasingsaidfirst register, relay means for connecting said first, said secondand said third groups of conductors to said rst, said second and saidthird registersl respectively, means including said relaymeans connectedto and controlled by-said' apparatus for connecting a source ofpotential toA a preselectedone of said first group-of conductors, meansincluding said rela-y means connected to and controlled by saidapparatusfor connecting said second group of conductors to said rstregister, and means including said relay means connected to andcontrolled by said-apparatus for connecting said third group ofconductors to said second register.

8. In atelephone system, a plurality of registers for registering thedigits of telephonic designations, register control means connected to afirst of said registers for setting said rst register, apparatusconnected to and controlled by the operation of said first register to acertain setting for releasing said nrst register, and means connected tosaid apparatus and tov said rst register effective When said firstregister is released after having beenoperated tosaid certain setting ctrol means for setting said first register, rst apisters to said controlmeans, second apparatus connected to said first register effective whensaid rst register is operated to said certain settings for releasingsaid rst register, means connected to said second apparatus and tosaidrst register eiective when said first register is released after havingbeen operated to said certain settings a second time for disabling saidsecond apparatus, and means connected to said first apparatus and tosaid first register eiective when said first register is released afterhaving been operated to said certain settings a second time forrendering said first apparatus eiective when said first register isoperated to any of its settings.

10. In a telephone system, a rst, a second and a third register forregistering the digits of telephonie designations, a rst, a second and athird group of output conductors, register control means, circuit meansconnecting said first register to said control means for setting saidrst register, apparatus connected to said rst register effective whensaid rst register is operated to a predetermined setting for releasingsaid ist register, relay means for connecting said rst, said second andsaid third groups of conductors to said first, said second and saidthird

